1. Field of the Invention
This invention relates to a skirt fairing, which is attachable beneath a lower, longitudinal edge of a trailer, and to methods for the production thereof. The present invention also relates to increased fuel efficiency and greater driving safety by deflecting and otherwise altering the airflow e.g., by creating laminar flow along the side and underneath the trailer of a tractor trailer rig or the like.
2. Description of the Prior Art
Modern cars are quite aerodynamically efficient but limited progress has been made with heavy-duty vehicles, trucks and the like. This is unfortunate principally because the fuel consumption by such a vehicle is high and any improvement in its aerodynamics performance is of great significance to transportation tractor-trailer rigs of the transportation industry in improving fuel economy. Acceleration and speed are, in general, of little interest in trucking. Existing performance in these fields is considered adequate. However fuel consumption is a major concern. It has recently been suggested that higher fuel prices, coupled with intense competition, may have the effect of closing down certain carriers. As the trailer of a large tractor-trailer rig is pulled forward by the tractor, a great deal of turbulence is created along the side and underneath the trailer as the vehicle disturbs the air. This turbulence results in increased resistance to forward movement of the tractor-trailer rigs, and thus to lower fuel efficiency. Work in a Low Speed Aerodynamics Laboratory in the early 1980's had demonstrated that smaller, but useful; drag reductions were still available from other treatments to the truck body or trailers than fairings or deflectors. These consisted of skirts that closed the body sides down toward the ground and beveled panels that reduced base drag. The skirts could provide a drag coefficient reduction of 0.06 per trailer on a tractor-trailer combination or about 0.02 on a straight truck. The rear panels (or the equivalent body beveling that has been used on buses) can produce a drag coefficient reduction of 0.06 on a straight truck, 0.08 on a bus, but only 0.04 on a trailer. The reason for the poor performance on the trailer is not known with certainty but may relate to the high-drag configurations on which it was first tested. The lower drag straight truck and the even lower-drag bus have much larger savings from this modification.
Moving freight by highway trucks has been increasing in volume for several years, and it appears that it will continue to increase in the future. This method of freight handling has proved to be more efficient and quicker than any other means in a large majority of situations. Nevertheless, this method has need of further improvement. A large problem is the energy needed to overcome wind resistance. It has been recognized that, by streamlining, vehicles can accomplish great savings in fuel expenses. Eddy currents are produced underneath the truck and its trailers, which add to the wind resistance. There is thus a great need to provide a maximum streamlining effect in order to reduce fuel consumption and operating costs.
Trucks, and particularly tractor-trailer rigs having multiple rear wheels, present a high resistance to air flow with the rear wheels, suspension, and other mechanical components at the rear of the vehicle interfering with the smooth flow of air around and under the vehicle. This interference creates turbulence and a high aerodynamic drag, which results in high fuel use and a high cost of operation. Furthermore, the turbulent flow can affect the trailers ability to track behind the trailer. This reduced driving stability is most prevalent in high crosswind conditions or when the trailer is empty. Furthermore, the turbulent flow, caused by yaw angle air traveling across the trailer bottom and releasing from the downwind side, creates a hazard for the drivers of other vehicles when it is raining or snowing, or the roadway is wet, for in such a situation, the rain or snow and any water splashed up from the roadway by the tires swirls around the tires and is thrown outwardly by the tires themselves and by the turbulent air flow. When this splashing and spraying water strikes the windshields of other vehicles, it lowers visibility for such motorists, and can cause them to lose control of their vehicles. Further, the spray raised by the rear tires reduces the truck driver's vision of the rear of the truck, making it more difficult for the truck driver to handle his vehicle when it's moving in traffic it is therefore advisable to improve the visibility of the driver.
It is well known that the fuel efficiency of any motor driven vehicle is directly related to the aerodynamic structure of the tractor-trailer rig and the amount of atmospheric turbulence caused by the movement of the vehicle. The greater the air turbulence created by the vehicle the greater the resistance, and the more fuel required to move the vehicle. In today's economy, fuel efficiency is of major concern and is particularly relevant when considered in terms of large tractor trailers used for transporting goods wherein the cost of fuel consumed moving the goods directly affects the market price of the goods. It is well known that improving the aerodynamics of a vehicle improves many aspects of its performance, particularly acceleration, top speed, fuel economy tracking stability and tire wear, driver comfort and ease of driving in cross winds.
Although fuel efficiency has become a primary concern in the recent decade because of fuel cost, a second major consideration is that of increasing the safety of operation of tractor-trailer rigs, particularly from the point of view of safety of other motorists sharing the road with such rigs. A major disadvantage of tractor trailers on the highway is that, unaltered, the turbulent air flow beneath and behind a tractor trailer is generally in a direction transverse to that of the movement of the tractor trailer. This means that in wet or snowy conditions, mist and/or snow is thrown laterally of the trailer causing a vision and turbulence problem for any motorist passing or being passed by the tractor-trailer rig.
Many modifications and accessories have been developed to improve the streamline of the airflow around a combined tractor-trailer truck. It is known that the amount of fuel required to haul a trailer over long distances can be reduced by equipping the trailer with a suitable aerodynamic fairing. An important such design is in the form of side shield or fairings, which are extended between the side of the tractor cab and the side of the trailer to provide a smooth transition surface there between. The side shields or fairings streamline airflow past the void space between the tractor and trailer by eliminating turbulence, which increases drag on the truck. Side shields eliminate the yaw angle air between rear of the tractor and the front of the trailer. Without side shields the air travels across the trailer face and releases from the downwind side. One type of fairing is mounted beneath each of the trailer's lower, outer longitudinal edges to extend between the trailer wheel assembly and the wheels of the tractor unit used to haul the trailer. Improved fuel economy is achieved while the trailer is hauled at highway speeds over long distances with fairings or side skirts mounted as aforesaid. Useful drag reductions were also said to be provided by skirts that closed the body sides down towards the ground to provide a reduced drag coefficient, or by bevelled panels that reduced base drag. Rear panels or body bevelling also reduced the drag somewhat, but apparently, not as much as by the use of skirts.
Many patents have issued which purport to have solved the above-identified problems. Among them, are the following:
Grout, Sr. et al, U.S. Pat. No. 3,743,343 disclosed a baffle means to be mounted on the undercarriage of the trailer forward of its rear axle(s) which channeled the airflow toward the rear and in the direction generally perpendicular to the rotational axes of the wheels, to mitigate the turbulence discharge from beneath the trailer in a direction generally transverse the trailer's movement. Besides the baffle means mounted on the sides forward of the rear axle, the Grout patent also disclosed a so-called “coagulating means” which was mounted to the undercarriage of the trailer rearwardly of the rear axle and which was designed to gather any turbulent discharge and direct it downwardly towards the road or pavement, thus attempting to minimize lateral discharge.
U.S. Pat. No. 4,021,069, patented May 3, 1977 by Hersh provided an aerodynamic drag reducing apparatus for mounting on the bluff, forward face of the trailing element of an over the road vehicle. The apparatus comprises a contoured member carried on the forward face and extending outwardly there from with its point of maximum extension substantially aligned for Impingement by an air stream. The portion of the surface displaced above the point of maximum extension describes a perturbed paraboloid of revolution with the rearward portions of the apparatus describing three sides of rectangle for aerodynamic merging with the top and side edges of the trailing element.
U.S. Pat. No. 4,262,953, patented Apr. 21, 1981 by McErlane, provided an airfoil or deflector panel for being mounted ahead of the rearmost set of wheels of a vehicle such as a truck or tractor-drawn trailer to direct air flow in a manner which reduces the relatively negative air pressure normally occurring behind a moving vehicle. The surface of the deflector, which is presented in the direction of vehicle motion, has a bilateral or compound convex curve a deflector panel of compound convexity mounted just forward of the rear axle or axles of a tractor drawn trailer.
U.S. Pat. No. 4,486,046, patented Dec. 4, 1984, by Whitney et al taught an airstream deflector assembly that mounted on the underside of a large vehicle, e.g., a semi-trailer or the like, to reduce drag, improve fuel economy, and reduce turbulence of rain or snow on a roadway traveled by the vehicle. Such assembly included a main panel which was essentially flat and was situated well forward of the following tires of the vehicle and deflecting the airstream downwardly primarily below the following axle and centers of such following tires. Such main deflection panel had mounted thereon four lateral airstream deflectors, two outboardly and two inboardly of the panel which served to concentrate the deflected airstream laterally toward the following tires of the vehicle and away from the “tunnel” between the tires. Both the main deflection panel and lateral deflectors were preferably angularly adjustable, either manually or remotely, with the preferred angularity of the main panel being with it lying in a plane which intersected the following tires slightly below their axis of rotation, and with the preferred angularity of the lateral deflectors being with them lying in planes substantially intersecting the inner faces of the following tires of the vehicle, e.g. at preferred angles relative to the direction of movement of the vehicle.
U.S. Pat. No. 4,518,188, patented May 21, 1985, by Witten provided an airflow improvement device for improving aerodynamic characteristics of a tractor-trailer truck. Such improvement included a side panel extending between the side of the tractor and the side of the trailer. A first end of the side panel was fixed to one of the tractor or trailer and the other end of the side panel was slidably restrained in a pocket structure mounted to the other of the tractor or the trailer so that the side panel will bend to form a smooth curved transition surface between the sides of the tractor and the trailer when the truck articulates to make a turn.
U.S. Pat. No. 4,640,541, patented Feb. 3, 1987 by FitzGerald et al, provided an air deflector for the rear wheels of vehicles, e.g., trucks and trailers. The deflector consisted of a fairing suspended beneath the truck or trailer body immediately in front of the rear wheels and extending completely across the width of the body. The surface of the fairing was curved in both a lateral and a vertical direction to deflect impinging air and entrained water or snow around or under the wheels. In a preferred form, the device was formed with a plurality of generally vertical grooves angled toward the centerline of the vehicle. The grooves directed impinging air downwardly and between the rear wheels. The air deflector served to suppress splashing and spraying of water from the roadway and of rain or snow, and reduced aerodynamic drag to improve handling and reduce fuel consumption.
U.S. Pat. No. 4,746,160 patented May 24, 1988 by Wiesemeyer, was directed to a highway truck with a semi-trailer and taught streamlined skirts on both sides of the vehicle that extended immediately above ground level, between the wheels.
U.S. Pat. No. 5,689,384, patented Mar. 11, 1997, by Loewen provided a fairing for use on a trailer. The trailer had a first member of the first edge that was hingedly attached to the trailer of the first edge. A second member had a first edge also hingedly attached to the trailer at that edge. A third member had a first edge hingedly attached to the trailer and arranged adjacent to the second member. The third member was telescopically receivable within the second member. The fairing was arranged along the lower edge of a trailer, adjacent the wheel.
U.S. Pat. No. 5,921,617, patented Jul. 13, 1999 by Loewen et al provided a fairing attachable beneath a lower, outer longitudinal edge of a trailer. The fairing had longitudinally extending forward and rearward sections. The rearward section can be moved longitudinally to adjustably locate its rearward edge in a selected position forward of the trailer's wheel assembly. Such adjustable positioning occurred automatically if the rearward section was coupled to, and longitudinally movable with, the support frame for the trailer's wheel assembly, thus maintaining the rearward edge of the fairing in the selected position whenever the trailer's wheel assembly is longitudinally adjusted relative to the trailer. A hinge mechanism coupled between the trailer and the fairing allowed pivotal displacement of each fairing section between lowered and raised positions. The lowered position was for long distance haulage of the trailer in order to achieve fuel economy. The raised position was for situations in which the trailer must be maneuvered over ramps, uneven terrain, etc. which might contact the underside of or otherwise interfere with the fairing.
U.S. Pat. No. 6,257,655, patented Jul. 10, 2001 by G. L. Selby, et al provided a protective skirt for an open frame trailer adapted to transport vehicles. The trailer included a wheeled chassis supporting a frame and track assembly. The trailer had a front-end adapted to be mounted in towing engagement on a tractor truck, a rear end adapted for receiving vehicles to be carried, and a middle section including the frame and track superstructure for supporting the vehicles. The protective skirt included a pair of first skirt sections mounted one on each side of the chassis in screening position at the trailer front end, a pair of second skirt sections mounted on the chassis one on each side thereof in screening position at the trailer middle section, a pair of third skirt sections mounted in screening position one on each side of the chassis above the wheels, and a pair of fourth skirt sections mounted on the chassis one on each side in screening position at the trailer rear section. The skirt assembly protected vehicles carried on the trailer against damage from rocks and road debris.
U.S. Pat. No. 6,644,720, patented Nov. 11, 2003 by Long et al, provided a streamlined highway truck including a tractor with a cab having a roof and two side sections and a semi trailer having a front, a top and two side sections and being pivotally joined by a fifth wheel to the tractor. The tractor had a top panel extending from the roof to adjacent the front edge of the top of the semi trailer and two side panels extending from the side sections of the tractor to the front edges of the respective side sections of the semi trailer. The side panels extended vertically from adjacently above ground level to a juncture with the top panel. Each of the side panels included a rigid portion connected to the side section of the cab and a vertical strip portion hingedly connected to the rigid portions and adapted to swing outwardly to accommodate a specific angular relationship between the side panel of the tractor and the adjacent side section of the semi trailer. The strip portions were spring biased to remain aligned with their respective rigid portions. The semi trailer had side panels extending downwardly from the bottom of the side sections to adjacently above ground level from adjacent the tractor wheels under the front of the semi trailer to adjacent the semi trailer wheels adjacent the rear of the semi trailer. Each of the above patented devices, though providing improvements in the art, have failed to adequately provide an aerodynamic side panel structure which presented a durable and easy to use fixed structure for accomplishing airflow improvement around a tractor-trailer truck. Some disclosed structures used very rigid side panels, which were difficult to maintain in position, and were awkward to handle. Some structures required cumbersome tensioning means to maintain the skirt or deflector in position.